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TIFF and LibTiff Mail List Archive

Thread

2012.01.09 01:53 "[Tiff] resolution issue when converting jpeg to tiff", by Jingfei Hu
2012.01.09 03:57 "Re: [Tiff] resolution issue when converting jpeg to tiff", by Bob Friesenhahn
2012.01.10 20:31 "Re: [Tiff] resolution issue when converting jpeg to tiff", by Chris Cox
2012.01.11 01:36 "Re: [Tiff] resolution issue when converting jpeg to tiff", by Jingfei Hu

2012.01.11 01:36 "Re: [Tiff] resolution issue when converting jpeg to tiff", by Jingfei Hu

I solved the problem with changing the type of xres/yres from int to float. Anyway, I think it doesn't make any sense.

Cheers,

Jfhu

2012/1/11 Chris Cox <ccox@adobe.com>:

Sounds like Windows properties isn't looking up the resolution metadata correctly, and defaults to 96dpi.

But Photoshop's default is 72dpi, so that isn't a fair test. Try saving a document set to 300 dpi and see what each application shows.

Photoshop CS5 is compliant with EXIF JPEG standards, and does not write the obsolete JFIF resolution fields. if software is over 10 years old and  So failed to update to EXIF standards, they may be relying on the obsolete JFIF fields and not correctly reading the file resolution.

On 1/8/12 5:53 PM, "Jingfei Hu" <jingfei.hu@gmail.com> wrote:

Hi, everyone.

I've posted this question on www.stackoverflow.com, but got no proper answer. So I decide to put this question here.

Now I have some files whose suffix is .tif. However, I can't open it with libtiff(Tiff for Windows 3.8.2). It says bad magic number (0xd8ff). So I know these files aren't actually tiff files, they are jpeg files.

Then, I use libjpeg library to read these files. I need to convert these jpeg files into tiff files. I get the x-resolution and y-resolution using libexif(because libjpeg doesn't support this), says 72 dpi, and I use TIFFSetField to set the corresponding field of the tiff to be generated with no error occurred. But the x-resolution is 96dpi when I look up the property of the generated tiff using Windows Property(Right click on the tiff ->Property).

When I use the utility of libtiff, tiffinfo.exe, to look the information of generated tiff files, it returns (0,0) pixels/inch.

When I open this generated tiff files with Photoshop CS5, it says 72 dpi in image size dialog (opened with Ctrl+Alt+I).

I just doesn't know the reason. Is there a method to set the resolution so that tiffinfo could recognize the resolution correctly.

Hope make myself clear